1. Field of the Invention
The present invention relates to a process for producing a multi-layer molded product of thermoplastic resins.
2. Description of the Related Art
Multi-layer molded products as combinations of thermoplastic resins are conventionally well known, and the following methods are known as processes for producing them.
(1) A method for bonding sheets of thermoplastic resins preliminarily produced to each other (for example, as described in the Japanese Patent Application Laid-open Gazette No. Sho 63-104805), or a method for bonding such sheets at the same time as molding of the thermoplastic resins (for example, as described in the Japanese Patent Application Laid-open Gazette No. Sho 49-23261).
(2) A method by sandwich injection molding (for example, as described in the Japanese Patent Application Laid-open Gazette No. Sho 62-268618 corresponding to U.S. Ser. No. 862269 or in the Japanese Patent Application Laid-open Gazette No. Sho 63-309417 corresponding to U.S. Ser. No. 050680).
In addition, an example of a process for producing a multi-layer molded product consisting of a resin molded body and a skin material is the process as described in U.S. Pat. No. 5,154,872.
However, the methods in (1) described above need a lot of steps because they include molding of members preliminarily processed in the sheet form. The method in (2) described above needs high injection pressure and needs two mold-closing steps in order to obtain a two-layer molded product. Further, in the process described in above U.S. Pat. No. 5,154,872, supply pressure of resin is low and there are many losses of edges of the skin material.